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opticaltempest

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I am taking measurements off the screen of an analog oscilloscope in order to calculate voltage and frequency of a sinusoidal wave form. The volts per division is set to 0.50V, and the time per division is set to 0.50 ms.

I measure the vertical length of the trace to be 2.67 divisions. I measure the horizontal length of the trace to be 0.87 divisions. I will assume that I can estimate my measurement to within 1/100 of a division.

Now I must do the following calculations to get the voltage and period of the wave form:

2.67 divisions * 0.50 V = 1.335 V

0.87 divisions * 0.50 ms = 0.435 ms

According to rules of significant figures, my answers should be rounded to 1.34 V and 0.44 ms.

I measure the vertical length of the trace to be 2.67 divisions. I measure the horizontal length of the trace to be 0.87 divisions. I will assume that I can estimate my measurement to within 1/100 of a division.

Now I must do the following calculations to get the voltage and period of the wave form:

2.67 divisions * 0.50 V = 1.335 V

0.87 divisions * 0.50 ms = 0.435 ms

According to rules of significant figures, my answers should be rounded to 1.34 V and 0.44 ms.

**Why is the zero in 0.87 ignored as a significant figure?**I know for a fact that my estimated measurement of 0.87 is not 1.87, not 2.87, not 3.87, etc. It doesn't make sense to me that I keep 3 significant figures for the measured voltage and only 2 significant figures for the measured period when both measurements are being measured using the same device-the division tick marks on the screen of the oscilloscope.
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